Patterned organometallic photoresists and methods of patterning

ABSTRACT

A rinse process is described for processing an initially patterned structure formed with an organometallic radiation sensitive material, in which the rinse process can remove portions of the composition remaining after pattern development to make the patterned structure more uniform such that a greater fraction of patterned structures can meet specifications. The radiation sensitive material can comprise alkyl tin oxide hydroxide compositions. The rinsing process can be effectively used to improve patterning of fine structures using extreme ultraviolet light.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application62/746,808, filed Oct. 17, 2018, to Kocsis et al., entitled “PatternedOrganometallic Photoresists and Method of Patterning,” incorporatedherein by reference.

FIELD

The present disclosure relates to patterned organometallic photoresistsand methods of patterning organometallic photoresists on a substrateusing radiation based lithography, e.g., extreme ultraviolet (EUV)lithography or e-beam lithography.

BACKGROUND OF THE DISCLOSURE

Patterning technologies can be used to form semiconductor-based andother electronic devices having complex, fine structures. In the fieldsof micro- and nanofabrication, integrated circuits have become verysmall. This has been driven, in part, by the steady decrease in circuitsize and the increase in circuit componentry density.

Photolithography technologies have been used to fabricate andmanufacture such integrated circuits. In photolithography, thepatterning of photoresist generally involves several steps including:exposing the photoresist to a selected energy source, through a mask, torecord a latent image and then developing and removing selected regionsof the photoresist. The exposed regions of the photoresist aretransformed to make patterned regions selectively removable. For apositive-tone photoresist, the exposed regions are removed to leave theunexposed regions. For a negative-tone photoresist, the unexposedregions are removed to leave the exposed regions.

Extreme ultraviolet (EUV) lithography is a specific photolithographictechnology making possible the continued reduction in feature sizes insemiconductor manufacturing. The short wavelength (λ=13.5 nm) of EUVradiation allows generation of high density patterns of light and,thereby, fabrication of small, dense features by photolithography. Inthe EUV photolithographic process, the photoresist is deposited as athin film, exposed with a pattern of EUV radiation to create a latentimage, and then developed with a liquid, such as an organic solvent, toproduce a developed pattern of the resist.

SUMMARY

In a first aspect, the invention pertains to a method for forming apattern in a radiation sensitive organometallic resist film on a surfaceof a substrate, the method comprising rinsing an initial patternedstructure with a rinse solution to remove a portion of developedphotoresist to control pattern dimensions, quality, and/or resolutionand to form an adjusted patterned structure. The rinsing step generallycomprises removal of underexposed portions of the developed photoresist.In some embodiments, the initial patterned structure can be formed by(i) coating the surface of the substrate with an organometallicradiation sensitive resist material to form the radiation sensitiveresist film, (ii) exposing the radiation sensitive resist film topatterned radiation to form an exposed film with exposed portions andunexposed portions, and (iii) contacting the exposed film with adeveloping solution to form developed photoresist in which generallyeither the unexposed portions or the exposed portions are selectivelysoluble in the developing solution. The above summary is not intended todescribe each illustrated embodiment or every implementation of thepresent disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings included in the present application are incorporated into,and form part of, the specification. They illustrate embodiments of thepresent disclosure and, along with the description, serve to explain theprinciples of the disclosure. The drawings are only illustrative ofcertain embodiments and do not limit the disclosure.

FIG. 1 is a flow chart for a photolithographic process according toembodiments of the present disclosure.

FIG. 2 is a schematic perspective view of a radiation patternedstructure with a latent image.

FIG. 3 is a side plan view of the structure of FIG. 2.

FIG. 4 is a schematic perspective view of the structure of FIG. 2 afterdevelopment of the latent image to remove un-irradiated coating materialto form a patterned structure.

FIG. 5 is a side view of the patterned structure of FIG. 4.

FIG. 6 is a schematic perspective view of the structure of FIG. 2 afterdevelopment of the latent image to remove irradiated coating material toform a patterned structure.

FIG. 7 is a side view of the patterned structure of FIG. 6.

FIG. 8 is a set of four scanning electron micrographs arranged adjacentto each other with each of 32-nm pitch lines with 16-nm spacingpatterned via EUV lithography, in which a left most image involveddevelopment followed by no rinse treatment, an image second from theleft involving processing followed by a 10 second rinse with a rinsingsolution, an image third from the left involving processing followed bya 20 second rinse with a rinsing solution, and a right most imageinvolving processing followed by a 30 second rinse with a rinsingsolution.

FIG. 9 is an array of 16 scanning electron micrographs (SEM) of asilicon substrate with organometallic resist patterned via EUVlithography to form 32-nm pitch lines (P32) with the top four SEM imagescorresponding to 16 nm line spacing (DOM1), with the second row of fourSEM images corresponding to 17-nm line spacing (DOM2), with the thirdrow of SEM images corresponding to 19-nm line spacing (DOM4), and withthe fourth row of SEM images corresponding to 20-nm line spacing (DOM5),in which the four images in each row from left to right correspond to norinse, 10 second TMAH rinse, 20 second TMAH rinse, and thirty secondTMAH rinse, respectively.

While the embodiments of the disclosure are amenable to variousmodifications and alternative forms, specifics thereof have been shownby way of example in the drawings and will be described in detail. Itshould be understood, however, that the intention is not to limit thedisclosure to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the disclosure.

DETAILED DESCRIPTION

Improved processing of patterns formed using organometallic radiationsensitive compositions provides for improved uniformity andreproducibility of patterns formed with very fine lines. Organometallicbased radiation sensitive resists provide the ability to achieve theformation of very fine patterns, especially using extreme ultravioletlight. In particular, alkyl tin oxide hydroxide compositions can bedeployed with commercially acceptable processing approaches. Thesignificant EUV absorption of these compositions along with the abilityto achieve very high etch contrasts provides for the formation of veryfine patterning. Also, these compositions can function as eithernegative resists or positive resists. This unusual property of potentialprocessing as a positive resist and a negative resist has been exploitedthrough the use of sequential developers to improve the uniformity of alithographic pattern. In particular, a first development step can beperformed to form the pattern, and a second mild development directed tothe material not removed by the first development can clean up theinitial developed pattern with the second development solution. Thesecond development step can involve removal of partially irradiatedmaterial and edges of the pattern remaining after the first developmentstep. Generally, one development liquid is an organic solvent and thesecond development solution is an aqueous alkaline solution. In thisway, improved patterning can be accomplished that can reduce productrejection rate for failure to achieve performance according tospecification. The ability to reduce waste due to failure of a productcan provide significant value for commercial production.

The patterning to form small radiation based lithographic featuresinvolves projecting radiation, such as extreme ultraviolet radiation,through a mask based on the pattern onto a radiation sensitive material.Of course, the irradiation process is not a mathematically preciseprocess. Thus, near the edges of the pattern, there can be blurring ofthe pattern due to various potential causes, such as imperfections inthe mask and irradiation non-uniformities in general, as well asstochastic and/or process fluctuations. Thus, when the pattern isdeveloped using a developing solution, corresponding imperfections maybe present in the developed pattern. For the alkyl tin oxide hydroxidecompositions described herein, the un-irradiated composition isgenerally soluble in an organic solvent, and the irradiated resistgenerally is soluble in a basic (i.e., alkaline) aqueous solution. Thematerial remaining after a development step can be subjected to adeveloper designed to remove the remaining composition. By performing asecond differential development under mild conditions, such as a shortperiod of time, partially irradiated material can be removed along witha small amount of the remaining pattern based on the first developmentstep. The second development step tends to improve the uniformity of thepatterning process to reduce the failure of corresponding products tomeet specifications.

Patterning of very small features has been accomplished with recentlydeveloped organometallic radiation resist compositions. In particular,alkyl tin oxide hydroxide compositions provide desirable patterningperformance, based at least in part on a high EUV absorption associatedwith the tin and a very high etch contrast upon radiation drivenfragmentation of the alkyl-tin bond. The alkyl tin oxide hydroxidecompositions provide an added feature of being able to function aseither a negative resist, in which the radiation exposed regions remainafter an initial development, or as a positive resist, in which theunexposed regions remain after an initial development. In any case, thedevelopment process is intended to involve processing conditions that donot significantly alter the remaining portions of the structure. For thealkyl tin oxide hydroxide compositions, the negative resist patterningcan be performed with an organic solvent developing agent that dissolvesthe un-irradiated resist, and the positive resist patterning can beperformed with an aqueous alkaline composition that dissolves theirradiated resist. This ability to perform under negative toneprocessing or positive tone processing is effectively exploited in thepresent combined processing to yield a more consistent and uniformpattern on a very small scale.

For consistent patterning performance with improved compatibility withexisting process equipment, monoalkyl tin oxide hydroxide compositionshave been found to be particularly effective for small patternformation. The monoalkyl tin oxide hydroxide compositions are generallysynthesized from compositions represented by the formula RSnX₃, where Ris the alkyl group and X is a hydrolyzable group, such as NR′R″ (amidegroup) or OR₀ (alkoxide group), where R′, R″ and R₀ are hydrocarbylgroups. The reaction to form the alkyl tin oxide hydroxide can beperformed in solution or alternatively in situ after coating onto thesubstrate to be processed. While desired processing can evolve, thecurrent desired processing approach involves the deposition of amonoalkyl tin trialkoxide composition with subsequent in situ hydrolysisto form the oxide hydroxide composition with release of an alcohol vaporbyproduct that can be readily removed. The following discussion providesa more general discussion along with more details regarding the specificprocessing.

Referring to FIG. 1, in an outline of the present process for improvedfine patterning, a radiation based patterning process, e.g., an extremeultraviolet (EUV) lithographic process, photoresist material isdeposited or coated as a thin film on a substrate 01,pre-exposure/softbaked 02, exposed with a pattern of radiation to createa latent image 03, post-exposure baked 04, and then developed 05 with aliquid, typically an organic solvent, to produce a developed pattern ofthe resist. This process can leave residual, unexposed or underexposedorganometallic photoresist between the patterned features, which canskew the quality of the patterned profiles. Accordingly, the processaccording to embodiments of the present disclosure can further includerinsing 06 the photoresist to remove the residue. This process isdescribed in detail below.

Coating

A coating of the organometallic resist composition can be formed throughthe deposition of a precursor solution onto a selected substrate. Asubstrate generally presents a surface onto which the coating materialcan be deposited, and the substrate may comprise a plurality of layersin which the surface relates to an upper most layer. The substratesurface can be treated to prepare the surface for adhesion of thecoating material. Prior to preparation of the surface, the surface canbe cleaned and/or smoothed as appropriate. Suitable substrate surfacescan comprise any reasonable material. Some substrates of interestinclude, for example, silicon wafers, silica substrates, other inorganicmaterials, polymer substrates, such as organic polymers, compositesthereof and combinations thereof across a surface and/or in layers ofthe substrate. Wafers, such as relatively thin cylindrical structures,can be convenient, although any reasonable shaped structure can be used.Polymer substrates or substrates with polymer layers on non-polymerstructures can be desirable for certain applications based on their lowcost and flexibility, and suitable polymers can be selected based on therelatively low processing temperatures that can be used for theprocessing of the patternable organometallic materials described herein.Suitable polymers can include, for example, polycarbonates, polyimides,polyesters, polyalkenes, copolymers thereof and mixtures thereof. Ingeneral, it is desirable for the substrate to have a flat surface,especially for high resolution applications.

Organometallic radiation sensitive resists have been developed based onalkyl tin compositions, such as alkyltin oxide hydroxide, approximatelyrepresented by the formula R_(z)SnO_((2-z/2-x/2))(OH)_(x), where 0<x<3,0<z≤2, x+z≤4, and R is a hydrocarbyl group forming a carbon bond withthe tin atom. Particularly effective forms of these compositions aremonoalkytin oxide hydroxide, in which z=1 in the above formula. Alkyltin based photoresist materials are further described in U.S. Pat. No.9,310,684 to Meyers et al., entitled “Organometallic Solution Based HighResolution Patterning Compositions,” and U.S. Patent ApplicationPublication Nos. 2016/0116839 A1 to Meyers et al., entitled“Organometallic Solution Based High Resolution Patterning Compositionsand Corresponding Methods,” and 2017/0102612 A1 to Meyers et al.(hereinafter the '612 application), entitled “Organotin Oxide HydroxidePatterning Compositions, Precursors, and Patterning,” each of which areincorporated herein by reference.

In situ hydrolysis of alkyl tin amides and/or alkyl tin alkoxidesprovides for the deposition of alkyl tin oxide hydroxide compositions.The discussion herein focuses on the monoalkyl tin compositions,although the more general alkyl tin compositions can similarly be used.The hydrolysis and condensation reactions that can transform thecompositions with hydrolyzable groups (X), such as amide or alkoxidegroups, are indicated in the following reactions:RSnX₃+3 H₂O→RSn(OH)₃+3 HX,RSn(OH)₃→RSnO_((1.5-(x/2)))OH_(x)+(x/2)H₂O.If the hydrolysis products HX are sufficiently volatile, in situhydrolysis can be performed with water vapor during the substratecoating process with the corresponding removal of the by-product HX.

The monoalkyl tin triamide compositions generally can be represented bythe formula RSn(NR′)₃, where R and R′ are independently an alkyl or acycloalkyl with 1-31 carbon atoms with one or more carbon atomsoptionally substituted with one of more heteroatom functional groupscontaining O, N, Si, and/or halogen atoms or an alkyl or a cycloalkylfurther functionalized with a phenyl or cyano group. In someembodiments, R′ can comprise ≤10 carbon atoms and can be, for example,methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, or t-amyl.The R group can be a linear, branched, (i.e., secondary or tertiary atthe metal-bonded carbon atom), or cyclic hydrocarbyl group. Each R groupindividually and generally has from 1 to 31 carbon atoms with 3 to 31carbon atoms for the group with a secondary-bonded carbon atom and 4 to31 carbon atoms for the group with a tertiary-bonded carbon atom. Inparticular, branched alkyl ligands can be desirable for some patterningcompositions where the compound can be represented as R¹R²R³CSn(NR′)₃,where R¹ and R² are independently an alkyl group with 1-10 carbon atoms,and R³ is hydrogen or an alkyl group with 1-10 carbon atoms. As notedbelow, this representation of alkyl ligand R is similarly applicable tothe other embodiments generally with R¹R²R³CSn(X)₃, with X correspondingto the trialkoxide or triamide moieties. In some embodiments R¹ and R²can form a cyclic alkyl moiety, and R³ may also join the other groups ina cyclic moiety. Suitable branched alkyl ligands can be, for example,isopropyl (R¹ and R² are methyl and R³ is hydrogen), tert-butyl (R¹, R²and R³ are methyl), tert-amyl (R¹ and R² are methyl and R³ is —CH₂CH₃),sec-butyl (R¹ is methyl, R² is —CH₂CH₃, and R³ is hydrogen), neopentyl(R¹ and R² are hydrogen, and R³ is —C(CH₃)₃), cyclohexyl, cyclopentyl,cyclobutyl, and cyclopropyl. Examples of suitable cyclic groups include,for example, 1-adamantyl (—C(CH₂)₃(CH)₃(CH₂)₃ or tricyclo(3.3.1.13,7)decane bonded to the metal at a tertiary carbon) and 2-adamantyl(—CH(CH)₂(CH₂)₄(CH)₂(CH₂) or tricyclo(3.3.1.13,7) decane bonded to themetal at a secondary carbon). In other embodiments hydrocarbyl groupsmay include aryl or alkenyl groups, for example, benzyl or allyl, oralkynyl groups. In other embodiments the hydrocarbyl ligand R mayinclude any group consisting solely of C and H and containing 1-31carbon atoms. In summary, some examples of suitable alkyl groups bondedto tin include, for example, linear or branched alkyl (i-Pr ((CH₃)₂CH—),t-Bu ((CH₃)₃C—), Me (CH₃—), n-Bu (CH₃CH₂CH₂CH₂—)), cyclo-alkyl(cyclo-propyl, cyclo-butyl, cyclo-pentyl), olefinic (alkenyl, aryl,allylic), or alkynyl groups, or combinations thereof. In furtherembodiments suitable R groups may include hydrocarbyl groups substitutedwith hetero-atom functional groups including cyano, thio, silyl, ether,keto, ester, or halogenated groups or combinations thereof.

The alkyl tin trialkoxide compositions can be represented by the formulaRSn(OR⁰)₃. The alkyl tin trialkoxide can be synthesized from alkyl tintriamide, although U.S. patent application Ser. No. 15/950,292 to Edsonet al., entitled “Monoalkyl Tin Compounds with Low PolyalkylContamination, Their Compositions and Methods”, incorporated herein byreference, also describes the synthesis of monoalkyl tin trialkoxidesfrom alkyl triamido tin and other synthesis pathways that may be used.The alkyl triamido tin compositions can be represented by the formulaRSn(NR″COR′″)₃. The R groups in the formulas for the alkyl tintrialkoxide and alkyl triamido tin compositions can be the same R groupsas summarized above for the alkyl tin triamide compositions, and thecorresponding discussion of these R groups above is as if copied in thisparagraph in its entirety. The monoalkyl triamido tin compositions arenot discussed further herein. For the alkoxide ligands —OR⁰, the R⁰groups can be independently hydrocarbon groups with 1-10 carbon atoms,such as methyl groups, ethyl groups, or the like.

In general, any suitable coating process can be used to deliver theprecursor solution to a substrate. Suitable coating approaches caninclude, for example, spin coating, spray coating, dip coating, vapordeposition, knife edge coating, printing, such as inkjet printing andscreen printing, and the like. Vapor deposition is discussed in the '612application cited above. To form a precursor solution, the resistcomposition can generally be dissolved in a suitable organic solvent.While some process parameters are dependent on the specific compositionof the organometallic resist, for the tin based resists described above,tin concentrations generally can be in the range of about 1 mM to about1 M, in further embodiments from about 2 mM to about 750 mM, and inother embodiments from about 5 mM to about 500 mM by amount of tin. Someof these coating approaches form patterns of coating material during thecoating process, although the resolution available currently fromprinting or the like has a significantly lower level of resolution thanavailable from radiation based patterning, as described herein.

If patterning is performed using radiation, spin coating can be adesirable approach to cover the substrate relatively uniformly, althoughthere can be edge effects. In some embodiments, a wafer can be spun atrates from about 500 rpm to about 10,000 rpm, in further embodimentsfrom about 1000 rpm to about 7500 rpm and in additional embodiments fromabout 2000 rpm to about 6000 rpm. The spinning speed can be adjusted toobtain a desired coating thickness. The spin coating can be performedfor times from about 5 seconds to about 5 minutes and in furtherembodiments from about 15 seconds to about 2 minutes. An initial lowspeed spin, e.g. at 50 rpm to 250 rpm, can be used to perform an initialbulk spreading of the composition across the substrate. A back siderinse, edge beam removal step or the like can be performed with water orother suitable rinse to remove any edge bead. A person of ordinary skillin the art will recognize that additional ranges of spin coatingparameters within the explicit ranges above are contemplated and arewithin the present disclosure.

The thickness of the coating generally can be a function of theprecursor solution concentration, viscosity, and the spin speed. Forother coating processes, the thickness can generally also be adjustedthrough the selection of the coating parameters. In some embodiments, itcan be desirable to use a thin coating to facilitate formation of smalland highly resolved features. In some embodiments, the coating materialscan have an average dry thickness prior to rinsing of no more than about1 micron, in further embodiments no more than about 250 nanometers (nm),in additional embodiments from about 1 nanometers (nm) to about 50 nm,in other embodiments from about 1 nm to about 40 nm and in someembodiments from about 1 nm to about 25 nm. The rinsing process taughtherein reduces the thickness of the developed resist pattern, which maybe exposed or unexposed resist depending on the patterning performed.The rinsing process should generally not excessively remove materialfrom the developed resist pattern, but the initial thickness of the dryresist coating materials can be selected in anticipation of the rinseprocess. The ranges of post rinse and post development coating thicknessgenerally fall within the same ranges as presented above with therealization that the rinsing effectively reduces the upper limits of thepost rinse coating thickness to some degree based on the percent ofmaterial removed in the rinse.

A person of ordinary skill in the art will recognize that additionalranges of thicknesses within the explicit ranges above are contemplatedand are within the present disclosure. The thickness can be evaluatedusing non-contact methods of x-ray reflectivity and/or ellipsometrybased on the optical properties of the film.

The coating process itself can result in the evaporation of a portion ofthe solvent since many coating processes form droplets or other forms ofthe coating material with larger surface areas and/or movement of thesolution that stimulates evaporation. The loss of solvent tends toincrease the viscosity of the coating material as the concentration ofthe species in the material increases. An objective during the coatingprocess can be to remove sufficient solvent to stabilize the coatingmaterial for further processing. The solvent removal process may not bequantitatively controlled with respect to specific amounts of solventremaining in the coating material, and empirical evaluation of theresulting coating material properties generally can be performed toselect processing conditions that are effective for the patterningprocess.

Pre-Exposure Bake

While heating may not be needed for successful application of theprocess, it can be desirable to heat the coated substrate to speed theprocessing and/or to increase the reproducibility of the process. Forembodiments in which in situ hydrolysis is used to form the alkyl tinoxide hydroxide, the pre-exposure bake drives the hydrolysis to form theradiation sensitive patterning composition. In embodiments in which heatis applied to remove solvent and/or drive the hydrolysis, the coatingmaterial can be heated to temperatures from about 45° C. to about 150°C., in further embodiments from about 50° C. to about 130° C. and inother embodiments from about 60° C. to about 110° C. The heating forsolvent removal can generally be performed for at least about 0.1minute, in further embodiments from about 0.25 minutes to about 30minutes, and in additional embodiments from about 0.50 minutes to about10 minutes. A person of ordinary skill in the art will recognize thatadditional ranges of heating temperature and times within the explicitranges above are contemplated and are within the present disclosure. Forembodiments in which in situ hydrolysis is performed, the hydrolysis byproduct, such as an amine or alcohol, can be removed during this heatingstep if the byproduct is appropriately volatile.

Exposure

The coating material can be finely patterned using radiation. As notedabove, the composition of the precursor solution and thereby thecorresponding coating material can be designed for sufficient absorptionof a desired form of radiation. The absorption of the radiation resultsin transfer of energy that breaks the alkyl tin bonds so that at leastsome of the alkyl ligands are no longer available to stabilize thematerial. With the absorption of a sufficient amount of radiation, theexposed coating material condenses, i.e. forms an enhanced metaloxo-hydroxo network, which may involve water absorbed from the ambientatmosphere. The radiation generally can be delivered according to aselected pattern. The radiation pattern is transferred to acorresponding pattern or latent image in the coating material withirradiated areas and un-irradiated areas. The irradiated areas comprisecondensed coating material, and the un-irradiated areas comprisegenerally the as-formed coating material. Sharp edges can be formed upondevelopment of the coating material with the removal of theun-irradiated coating material.

Radiation generally can be directed to the coated substrate through amask or a radiation beam can be controllably scanned across thesubstrate. In general, the radiation can comprise electromagneticradiation, an electron beam (beta radiation), or other suitableradiation. In general, electromagnetic radiation can have a desiredwavelength or range of wavelengths, such as visible radiation,ultraviolet radiation or x-ray radiation. The resolution achievable forthe radiation pattern is generally dependent on the radiationwavelength, and a higher resolution pattern generally can be achievedwith shorter wavelength radiation. Thus, it can be desirable to useultraviolet light, x-ray radiation or an electron beam to achieveparticularly high resolution patterns.

Following International Standard ISO 21348 (2007) incorporated herein byreference, ultraviolet light extends between wavelengths of greater thanor equal 100 nm and less than 400 nm. A krypton fluoride laser can beused as a source for 248 nm ultraviolet light. The ultraviolet range canbe subdivided in several ways under accepted Standards, such as extremeultraviolet (EUV) from greater than or equal 10 nm to less than 121 nmand far ultraviolet (FUV) from greater than or equal to 122 nm to lessthan 200 nm. EUV light has been used for lithography at 13.5 nm, andthis light is generated from a Xe or Sn plasma source excited using highenergy lasers or discharge pulses. The monoalkyl tin oxide hydroxidebased radiation sensitive compositions have been found to provideparticularly effective resists for EUV and e-beam patterning, which aredomains in which traditional organic resists have been considered to notdeliver the full patterning capabilities of these lithographicprocesses.

The amount of electromagnetic radiation can be characterized by afluence or dose which is obtained by the integrated radiative flux overthe exposure time. Suitable radiation fluences can be from about 1mJ/cm² to about 150 mJ/cm², in further embodiments from about 2 mJ/cm²to about 100 mJ/cm² and in further embodiments from about 3 mJ/cm² toabout 50 mJ/cm². In an embodiment, the EUV radiation can be done at adose of less than or equal to about 100 mJ/cm² or with an electron beamat a dose equivalent to or not exceeding about 2 mC/cm² at 30 kV. Aperson of ordinary skill in the art will recognize that additionalranges of radiation fluences within the explicit ranges above arecontemplated and are within the present disclosure.

With electron beam lithography, the electron beam generally inducessecondary electrons which generally modify the irradiated material. Theresolution can be a function at least in part of the range of thesecondary electrons in the material in which a higher resolution isgenerally believed to result from a shorter range of the secondaryelectrons. Based on high resolution achievable with electron lithographyusing the organometallic coating materials described herein, the rangeof the secondary electrons in the organometallic material is limited.Electron beams can be characterized by the energy of the beam, andsuitable energies can range from about 5 eV to about 200 keV and infurther embodiments from about 7.5 eV to about 100 keV.Proximity-corrected beam doses at 30 keV can range from about 0.1microcoulombs per centimeter squared (μC/cm²) to about 5 millicoulombsper centimeter squared (mC/cm²), in further embodiments from about 0.5μC/cm² to about 1 mC/cm² and in other embodiments from about 1 μC/cm² toabout 100 μC/cm². A person of ordinary skill in the art can computecorresponding doses at other beam energies based on the teachings hereinand will recognize that additional ranges of electron beam propertieswithin the explicit ranges above are contemplated and are within thepresent disclosure.

Following exposure with radiation, the coating material is patternedwith irradiated regions and un-irradiated regions. Referring to FIGS. 2and 3, a patterned structure 100 is shown comprising a substrate 102, athin film 103 and patterned coating material 104. Patterned coatingmaterial 104 comprises condensed regions 110, 112, 114, 116 ofirradiated coating material and regions and uncondensed regions 118,120, 122 of un-irradiated coating material. The patterned formed bycondensed regions 110, 112, 114, 116 and uncondensed regions 118, 120represent a latent image in to the coating material.

Based on the design of the organometallic coating material, there is alarge contrast of material properties between the irradiated regionsthat have condensed coating material and the un-irradiated, uncondensedcoating material. It has been surprisingly found that the contrast canbe improved with a post-irradiation heat treatment, althoughsatisfactory results can be achieved in some embodiments withoutpost-irradiation heat treatment. The post-exposure heat treatment seemsto anneal the irradiated coating material to improve its condensationwithout significantly condensing the un-irradiated regions of coatingmaterial.

Post-Exposure Bake

After completion of the exposure step, the coating materials can be heattreated to increase the etch contrast through further condensation ofthe exposed radiation sensitive composition. In some embodiments, thepatterned coating material can be heated at a temperature from about 90°C. to about 600° C., in further embodiments from about 100° C. to about400° C. and in additional embodiments from about 125° C. to about 300°C. The heating can be performed for at least about 10 seconds, in otherembodiment for about 15 seconds to about 30 minutes, and in furtherembodiments from about 20 seconds to about 15 minutes. A person ofordinary skill in the art will recognize that additional ranges oftemperatures and time for the heat treatment within the explicit rangesabove are contemplated and are within the present disclosure. This highcontrast in material properties further facilitates the formation ofsharp lines in the pattern following development as described in thefollowing section.

Development

With respect to negative tone imaging, referring to FIGS. 4 and 5, thelatent image of the structure shown in FIGS. 2 and 3 has been developedthrough contact with a developer to form patterned structure 130. Afterdevelopment of the image, thin film 103 is exposed along the top surfacethrough openings 132, 134, 135. Openings 132, 134, 135 are located atthe positions of uncondensed regions 118, 120, 122 respectively. Withrespect to positive tone imaging, referring to FIGS. 6 and 7, the latentimage of the structure shown in FIGS. 2 and 3 has been developed to formpatterned structure 140. Patterned structure 140 has the conjugate imageof patterned structure 130. Patterned structure 140 has thin film 103exposed at positions of irradiated regions 110, 112, 114, 116 that aredeveloped to form openings 142, 144, 146, 148.

The coating compositions with organic-stabilization ligands produce amaterial that is inherently hydrophobic. Irradiation to break at leastsome of the organic metal bonds converts the material into a lesshydrophobic, i.e., more hydrophilic, material. This change in characterprovides for a significant contrast between the irradiated coating andnon-irradiated coating that provides for the ability to do both positivetone patterning and negative tone patterning with the same resistcomposition. Specifically, the irradiated coating material condenses tosome degree into more of a metal oxide composition; however, the degreeof condensation generally is moderate without significant heating sothat the irradiated material is relatively straightforward to developwith convenient developing agents.

For the negative tone imaging, the developer can be an organic solvent,such as the solvents used to form the precursor solutions. In general,developer selection can be influenced by solubility parameters withrespect to the coating material, both irradiated and non-irradiated, aswell as developer volatility, flammability, toxicity, viscosity andpotential chemical interactions with other process material. Inparticular, suitable developers include, for example, aromatic compounds(e.g., benzene, xylenes, toluene), esters (e.g., propylene glycolmonomethyl ester acetate, ethyl acetate, ethyl lactate, n-butyl acetate,butyrolactone), alcohols (e.g., 4-methyl-2-pentanol, 1-butanol,isopropanol, 1-propanol, methanol), ketones (e.g., methyl ethyl ketone,acetone, cyclohexanone, 2-heptanone, 2-octanone), ethers (e.g.,tetrahydrofuran, dioxane, anisole) and the like. The development can beperformed for about 5 seconds to about 30 minutes, in furtherembodiments from about 8 seconds to about 15 minutes and in additionembodiments from about 10 seconds to about 10 minutes. A person ofordinary skill in the art will recognize that additional ranges withinthe explicit ranges above are contemplated and are within the presentdisclosure.

For positive tone imaging, the developer generally can be aqueous acidsor bases. In some embodiments, aqueous bases can be used to obtainsharper images. To reduce contamination from the developer, it can bedesirable to use a developer that does not have metal atoms. Thus,quaternary ammonium hydroxide compositions, such as tetraethylammoniumhydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxideor combinations thereof, are desirable as developers. In general, thequaternary ammonium hydroxides of particular interest can be representedwith the formula R₄NOH, where R=a methyl group, an ethyl group, a propylgroup, a butyl group, or combinations thereof. The coating materialsdescribed herein generally can be developed with the same developercommonly used presently for polymer resists, specifically tetramethylammonium hydroxide (TMAH). Commercial TMAH is available at 2.38 weightpercent, and this concentration can be used for the processing describedherein. Furthermore, mixed quaternary tetraalkyl-ammonium hydroxides canbe used. In general, the developer can comprise from about 0.5 to about30 weight percent, in further embodiments from about 1 to about 25weight percent and in other embodiments from about 1.25 to about 20weight percent tetra-alkylammonium hydroxide or similar quaternaryammonium hydroxides. A person of ordinary skill in the art willrecognize that additional ranges of developer concentrations within theexplicit ranges above are contemplated and are within the presentdisclosure.

For the improved processing described herein, a rinse agent can be theopposite, in the sense of negative tone versus positive development,developer. So if a negative tone pattern is formed, a rinse can beperformed with a positive tone developer composition to improve theimage, as exemplified below. Similarly, if a positive tone pattern isdeveloped a mild rinse with a negative tone development agent can beused. The rinsing process is described further in the following section.

In addition to the primary developer composition, the developer cancomprise additional compositions to facilitate the development process.Suitable additives include, for example, dissolved salts with cationsselected from the group consisting of ammonium, d-block metal cations(hafnium, zirconium, lanthanum, or the like), f-block metal cations(cerium, lutetium or the like), p-block metal cations (aluminum, tin, orthe like), alkali metals (lithium, sodium, potassium or the like), andcombinations thereof, and with anions selected from the group consistingof fluoride, chloride, bromide, iodide, nitrate, sulfate, phosphate,silicate, borate, peroxide, butoxide, formate,ethylenediamine-tetraacetic acid (EDTA), tungstate, molybdate, or thelike and combinations thereof. If the optional additives are present,the developer can comprise no more than about 10 weight percent additiveand in further embodiments no more than about 5 weight percent additive.A person of ordinary skill in the art will recognize that additionalranges of additive concentrations within the explicit ranges above arecontemplated and are within the present disclosure. The additives can beselected to improve contrast, sensitivity and line width roughness. Theadditives in the developer can also inhibit formation and precipitationof metal oxide particles.

With a weaker developer, e.g., lower concentration developer, a highertemperature development process can be used to increase the rate of theprocess. With a stronger developer, the temperature of the developmentprocess can be lower to reduce the rate and/or control the kinetics ofthe development. In general, the temperature of the development can beadjusted between the appropriate values of an aqueous solvent.Additionally, developer with dissolved organometallic coating materialnear the developer-coating interface can be dispersed withultrasonication during development.

The developer can be applied to the patterned coating material using anyreasonable approach. For example, the developer can be sprayed onto thepatterned coating material, or the structure can be dipped or otherwiseimmersed in the developer. Also, spin coating can be used. For automatedprocessing, a puddle method can be used involving the pouring of thedeveloper onto the coating material in a stationary format. If desiredspin rinsing and/or drying can be used to complete the developmentprocess. After the image is developed, the coating material is disposedon the substrate as a pattern.

Rinsing

As discussed above, after the step of development, there can beresidual, unexposed, or underexposed photoresist between patternedfeatures. This residue can skew the quality of the patterned profilesand affect the efficacy of subsequent pattern transfer processes basedon etching. As described herein, a rinse step can be used to remove suchresidue. For embodiments based on negative development, a rinse in anaqueous quaternary ammonium hydroxide, such as aqueoustetramethylammonium hydroxide (TMAH), after development in an organicsolvent can effectively remove photoresist residue to enhance patternfidelity and reduce or eliminate microbridge defects. Such rinsing canbe accomplished by any of a number of rinsing methods, including, by wayof example, (i) immersion of wafers into a bath, (ii) dispensing therinse solution though spray nozzles directly onto the wafer, and (iii)placing the wafer into an overflowing rinse tank. For automatedprocessing, the rinse can be performed, for example, with a puddlemethod in which the rinse solution is deposited on the wafer surface,and spun or blown dry to complete the rinse process. A person ofordinary skill in the art will recognize that other rinsing methods arecontemplated and are within the present disclosure.

To rinse the negative patterned substrate, an alkaline rinse agent canbe used. To avoid the introduction of metals, it can be desirable to usea quaternary ammonium hydroxide, such as are described above asdevelopers of a positive resist. In some embodiments, the rinse solutioncan comprise between from about 0.5 to about 30 weight percent, infurther embodiments from about 1 to about 25 weight percent and in otherembodiments from about 1.25 to about 20 weight percenttetra-alkylammonium hydroxide or similar quaternary ammonium hydroxides.In yet further embodiments, the rinse solution comprises 2.38% w/wtetramethylammonium hydroxide (TMAH). A person of ordinary skill in theart will recognize that additional ranges of concentrations oftetramethylammonium hydroxide (TMAH) can be used.

As demonstrated in the examples below, the rinse time can be adjusted toachieve a desired improvement in pattern uniformity as well as selectinga line width. A selected rinse time can also be influenced by the rinseagent concentration and rinse temperature. Based on suitable processtimes for automated processing, generally the rinse times can bedesigned to be from at least about a second, in other embodiments fromabout 2 seconds to about 30 minutes, in further embodiments from about 4seconds to about 20 minutes, and in other embodiments from about 6seconds to about 5 minutes. A person of ordinary skill in the art willrecognize that additional ranges of rinse times within the explicitranges above are contemplated and are within the present disclosure. Therinse generally is believed to reduce the thickness of the patternedresist. The amount of thickness of patterned resist is expected to beroughly similar to half the magnitude of the line width narrowing sincethe line width is narrowed from both directions. If desired, thethickness deposited for the resist can be correspondingly adjusted, buta small decrease in pattern thickness may not alter further processing.Following rinsing, the patterned structure can be used to deposit ontoor etch from the substrate as a step to product formation.

Pitch can be evaluated by design and confirmed with scanning electronmicroscopy (SEM), such as with a top-down image. As used herein, pitchrefers to the spatial period, or the center-to-center distances ofrepeating structural elements, and as generally used in the art ahalf-pitch is a half of the pitch. Feature dimensions of a pattern canalso be described with respect to the average width of the feature,which is generally evaluated away from corners or the like. Also,features can refer to gaps between material elements and/or to materialelements. The rinse can be used to decrease the widths of features whilecorrespondingly increasing the gap while removing bridges andimperfections from the initial development. Average line-width roughnesscan be no more than about 5 nm and in some embodiments no more thanabout 4.8 nm. Evaluating line-width roughness is performed by analysisof top-down SEM images to derive a 3σ deviation from the meanline-width. The mean contains both high-frequency and low-frequencyroughness, i.e., short correlation lengths and long correlation lengths,respectively. The line-width roughness of organic resists ischaracterized primarily by long correlation lengths, while the presentorganometallic coating materials exhibit significantly shortercorrelation lengths. In a pattern transfer process, short correlationroughness can be smoothed during the etching process, producing a muchhigher fidelity pattern. A person of ordinary skill in the art willrecognize that additional ranges of pitch, average widths and line-widthroughness within the explicit ranges above are contemplated and arewithin the present disclosure. Based on these processes, the patterningcan be adapted to the formation of various devices such as electronicintegrated circuits, generally through the repeated patterning processto form appropriately layered structures, such as transistors or othercomponents.

EXAMPLES

Resist patterns based on negative-tone development after EUV exposurewere used in the following examples. Referring specifically to FIG. 1,following the steps were followed: coat 01, bake 02, expose 03, bake 04,develop 05, and rinse 06 (except comparative examples based on controlsamples did not undergo any rinse). Rinse times for a set of patternsare examined.

Coating—An alkyl tin photoresist product (Inpria, Oreg., USA) was spincoated on a 300-mm diameter silicon wafer at 1307 rpm for 40 seconds.The photoresist product was an alkyl tin trialkoxide composition in analcohol solvent as described in the '612 application.

Pre-Exposure Bake—The coated substrate was then baked on a hotplate at100° C. for one (1) minute in an ambient atmosphere. Previous studieshave suggested that such processing in the ambient air results inhydrolysis of the tin-alkoxide ligands to form the alkyl tin oxidehydroxide composition in situ. Ellipsometry was used to indicate thatthe film thickness was approximately 22 nm after the bake.

Exposure—The coated substrate was then exposed to EUV radiation with anASML NXE3350 tool with Dipole90 Sigma 0.878/0.353 applied. Thesubstrates were exposed via four different masks with various spacingbetween patterned lines. Each mask had patterned lines spaced at a pitchof 32 nm. The first set of examples had 16 nm of open space between thepatterned lines. The second, third, and fourth examples had 17 nm, 19nm, and 20 nm of open space between the patterned lines, respectively.Masks with larger open spaces can reflect more EUV light and, therefore,deliver a higher exposure dose to the photoresist in a set exposuretime.

Post-Exposure Bake—After exposure, the coatings were subjected to apost-exposure bake (PEB) at 170° C. for one (1) minute.

Development—The exposed and baked films were then dipped in 2-heptanone(TOK, >99%) for approximately forty (40) seconds to remove unexposedportions of the photoresist film and to develop a negative-tone pattern.

Rinse—After development, each of the patterned films was then treated in2.38% w/w aqueous TMAH solution for periods ranging from 10 to 30seconds. Such rinsing was done by soaking the coated substrates in 2.38%w/w aqueous TMAH solution. The comparative examples did not undergo anyrinsing with TMAH.

Example 1—32 nm Pitch, 16 nm Spacing with No Rinse, 10 s, 20 s, or 30 sRinse Times

This example demonstrates the formation of a resist pattern based onnegative-tone development after EUV exposure with a comparison ofpatterning results following development with no TMAH rinse or a rinsewith a selected rinse time.

Four sets of patterned samples are discussed based on a pitch ofpatterned lines of 32 nm and an open space between the lines of 16 nm.The four samples had no rinse or rinse times of approximately ten (10)seconds, twenty (20) seconds, or thirty (30) seconds, respectively.Following the rinse, the four samples had line widths and line widthroughnesses as follows:

a) No rinse—20.8 nm and 7.8 nm (FIG. 8, 1st image from left)

b) 10 s Rinse Time—19.2 nm and 5.9 nm (FIG. 8, 2nd image);

c) 20 s Rinse Time—16.9 nm and 5.0 nm (FIG. 8, 3rd image from left); and

d) 30 s Rinse Time—14.6 nm and 4.4 nm (FIG. 8, fourth image from left).

The progressively decreasing line width as the samples are rinsed for alonger period of time reflects the removal of unexposed and underexposedphotoresist residue along the edges of the pattern and elimination ofmicrobridge defects. The resulting more uniform structure is visible inthe scanning electron micrographs of FIG. 8. The line widths alsodecrease as a result of the rinse. A corresponding small decrease inheight of the remaining resist composition is believed to take place,but the post rinse pattern height was not measured.

Example 2—32 nm Pitch with Various Line Spacings, with No Rinse, 10 s,20 s, or 30 s Rinse Time

This example demonstrates the effect of a post development alkalinerinse on samples prepared with a range of line spacings.

The samples in this example had a pitch of patterned lines of 32 nm, andline widths (pre-rinse line widths) of 16 nm, 17 nm, 19 nm or 20 nm. Foreach line width, different samples were subjected to rinse times ofapproximately ten (10) seconds, twenty (20) seconds or thirty (30)seconds, respectively. Control samples (CS) were prepared without arinse for comparison. Following the rinse, the samples were evaluated bySEM to determine post rinse line widths and line width roughnesses. SeeFIG. 9. The results are presented in Table 1.

TABLE 1 Line Line Width - pre Width - post Line Width Sample (nm) RinseTime (s) (nm) Roughness (nm) CS1 16 0 16.3 3.8 1 16 10 14.7 3.8 2 16 2011.4 4.1 3 16 30 9.7 4.2 CS2 17 0 17.6 3.9 4 17 10 15.8 3.9 5 17 20 12.84.1 6 17 30 11.1 4.1 CS3 19 0 20.8 7.8 7 19 10 19.2 5.9 8 19 20 16.9 5.09 19 30 14.6 4.4 CS4 20 0 21.0 9.4 10  20 10 20.4 7.5 11  20 20 19.0 5.512  20 30 17.0 4.7

The progressively decreasing line width as the samples are rinsed for alonger period of time reflects the removal of unexposed and underexposedphotoresist residue and elimination of microbridge defects. The controlsamples (CS1-CS4) provide the nominal line widths directly resultingfrom the initial patterning.

As can be seen by the examples, a wide process window is available toproduce a line-space pattern with targeted dimensions. If a user desiresa certain feature size/width, the user can select a mask size (pitchand/or line spacing), solution, and rinse duration to obtain the desiredfeature size/width. By way of example, if a user desires a featuresize/width of about 13 nm and the user has a mask with a pitch of 32 nmand line width of 17 nm, the user can rinse the patterned film in a2.38% w/w aqueous TMAH solution for a periods of about twenty (20)seconds to obtain the desired feature size/width of 13 nm. Prior to therinse, the feature would have a line width of about 17.61 nm.

The embodiments above are intended to be illustrative and not limiting.Additional embodiments are within the claims. In addition, although thepresent invention has been described with reference to particularembodiments, those skilled in the art will recognize that changes can bemade in form and detail without departing from the spirit and scope ofthe invention. Any incorporation by reference of documents above islimited such that no subject matter is incorporated that is contrary tothe explicit disclosure herein. To the extent that specific structures,compositions and/or processes are described herein with components,elements, ingredients or other partitions, it is to be understood thatthe disclosure herein covers the specific embodiments, embodimentscomprising the specific components, elements, ingredients, otherpartitions or combinations thereof as well as embodiments consistingessentially of such specific components, ingredients or other partitionsor combinations thereof that can include additional features that do notchange the fundamental nature of the subject matter, as suggested in thediscussion, unless otherwise specifically indicated.

What is claimed is:
 1. A method for forming an adjusted patternedstructure, the method comprising rinsing an initial patterned structurewith a rinse solution to remove a portion of developed photoresist tocontrol pattern dimensions and to form an adjusted patterned structure,wherein the initial patterned structure was formed by (i) coating thesurface of the substrate with an organometallic radiation sensitiveresist material to form the radiation sensitive resist film, (ii)exposing the radiation sensitive resist film to patterned radiation toform an exposed film with exposed portions and unexposed portions, and(iii) contacting the exposed film with a developing solution to form adeveloped photoresist wherein either the exposed portions or theunexposed portions are selectively soluble in the developing solution.2. The method of claim 1 wherein the rinse solution comprises aqueousquaternary ammonium hydroxide and the developing solution comprises anorganic solvent.
 3. The method of claim 1 wherein the developingsolution comprises aqueous quaternary ammonium hydroxide and the rinsesolution comprises an organic solvent.
 4. The method of claim 1 whereinthe rinse solution is about 0.5 to 30 weight percent aqueous tetramethylammonium hydroxide (TMAH).
 5. The method of claim 1 wherein theorganometallic radiation sensitive resist material comprises an alkyltinoxide hydroxide approximately represented by the formulaR_(z)SnO_((2-z/2-x/2))(OH)_(x), where 0<x<3, 0<z≤2, x+z≤4, and R is ahydrocarbyl group forming a carbon bond with the tin atom.
 6. The methodof claim 1 wherein the organometallic radiation sensitive resistmaterial comprises monoalkytin oxide hydroxide.
 7. The method of claim 1wherein the developing solution comprises a ketone.
 8. The method ofclaim 1 wherein the developing solution comprises 2-heptanone.
 9. Themethod of claim 1 wherein the substrate is a silicon wafer.
 10. Themethod of claim 1 wherein the radiation sensitive resist film is exposedto extreme ultraviolet radiation at a dose of no more than about 100mJ/cm² or with an electron beam at a dose no more than about 2 mC/cm² at30 kV.
 11. The method of claim 1 wherein the patterned structure has aninitial dry thickness prior to the step of rinsing, and a final drythickness after the step of rinsing, wherein the initial dry thicknessis from about 1 nm to about 50 nm and the final dry thickness is fromabout 1 nm to about 50 nm.
 12. The method of claim 1 wherein the rinsesolution is about 0.5 to about 30 weight percent aqueous tetramethylammonium hydroxide, aqueous tetrapropylammonium hydroxide, aqueoustetrabutylammonium hydroxide, or combinations thereof.
 13. The method ofclaim 1 wherein the initial patterned structure is rinsed with therinsing solution for at least about one (1) second.
 14. The method ofclaim 1 wherein a duration of rinsing and a concentration of the rinsesolution are selected to produce a desired feature size of the patternedstructure.
 15. The method of claim 1 wherein the rinsing solutioncomprises tetramethylammonium hydroxide (TMAH), and wherein a spacesizing and a pitch of the patterned radiation, duration of rinse, and aconcentration of the TMAH in the solution are selected to produce adesired feature size and/or resolution of the adjusted patternedstructure.
 16. The method of claim 1 wherein the adjusted patternedstructure has an average line-width roughness that is no more than about5 nm.
 17. The method of claim 1 further comprising: either a step of A)depositing a material based on the adjusted patterned structure or B)etching the substrate based on the adjusted patterned structure; andremoving the adjusted patterned structure to form a processed substrate.18. The method of claim 17 further comprising forming a subsequentpatterned structure on the processed substrate.
 19. The method of claim1 further comprising forming the initial patterned structure wherein thedeveloping solution comprises an organic solvent and wherein the rinsesolution comprises a quaternary ammonium hydroxide.
 20. The method ofclaim 1 wherein the rinsing step is performed using a puddle methodwherein the rinsing solution is applied to the surface of the initialpatterned structure and dried by spinning and/or blowing following aselected period of time.
 21. The method of claim 1 wherein the radiationsensitive resist material comprises a monoalkyl tin oxide hydroxide. 22.The method of claim 21 wherein the radiation sensitive resist materialis exposed to extreme ultraviolet radiation at a dose of no more thanabout 100 mJ/cm², the initial dry thickness of the patterned structureis no more than about 50 nm, and wherein a duration of rinse andconcentration of the rinsing solution are selected to produce a desiredfeature size and/or resolution of the patterned structure.
 23. Themethod of claim 1 wherein the radiation sensitive resist material issuitable for either positive tone or negative tone development, andwherein if the initial pattern is formed using a developer to form anegative tone pattern, the rinse composition comprises a suitablecomposition to perform positive development of the radiation sensitiveresist material, or if the initial pattern is formed with a developer toform a positive tone pattern, the rinse composition comprises a suitablecomposition to form a negative tone pattern.